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FISHERY BOARD OF SWEDEN
INSTITUTE OF FRESHWATER RESEARCH
DROTTNINGHOLM
Report No 54
LUND 1975
CARL BLOMS BOKTRYCKERI A.-B.
FISHERY BOARD OF SWEDEN
INSTITUTE OF FRESHWATER RESEARCH
DROTTNINGHOLM Report No 54
LUND 1975
CARL BLOMS BOKTRYCKERI A.-B.
Contents
Muscle and Blood Lactate in Juvenile Salmo salar Exposed to High pCOg; Hans Börjeson and Lars B. Höglund ... 5 The Acidification of Swedish Lakes; William Dickson ... 8 Possible Odour Responses of Juvenile Arctic Char (Salvelinus alpinus (L.)) to Three Other
Species of Subarctic Fish; LarsB. Höglund, Anders Bohmanand Nils-Arvid Nilsson 21 Population Biology of the Cestode Caryophyllaeus laticeps (Pallas) in Bream, Abramis
brama (L.), and the Feeding of Fish on Oligochaetes; Göran Milbrink... 36 Some Effects of Acidification on Roe of Roach, Rutilus rutilus L., and Perch, Perea fluvi-
atilis L. with Special Reference to the Ävaå Lake System in Eastern Sweden; Göran Milbrink and Niklas Johansson ... 52 Behaviour of Fish Influenced by Hotwater Effluents as Observed by Ultrasonic Tracking;
Lennart Nyman ... 63 Allelic Selection in a Fish (Gymnocephalus cernua (L.)) subjected to Hotwater
Effluents; Lennart Nyman ... 75 Pike as the Test Organism for Mercury, DDT and PCB Pollution. A Study of the Conta
mination in the Stockholm Archipelago; Mats Olsson and Sören Jensen ... 83 On Long-Term Stability of Zooplankton Composition; Birger Pejler ... 107 A Note on the Aggressive Behaviour of Adult Male Sea Trout Towards “Precocious” Males
During Spawning; Torgny Bohlin ... Ug
Muscle and Blood Lactate in Juvenile Salmo salar Exposed to High pCOa
HANS BÖRJESON and LARS B. HÖGLUND Institute of Zoophysiology,
University of Uppsala, Sweden
I. INTRODUCTION
Transitory acidosis in salmon parr due to hyper
capnia brought about by a sudden increase in pC02 in the ambient water has been described by Höglund and Börjeson (1971). According to earlier observations by Höglund and Härdig
(1969) young salmon also respond to a raised environmental pCO, by transitory agitated swim
ming and hyperventilation. Höglund and Börje
son (op. cit.) found no statistically significant increase in the blood lactate content during this initial phase of carbon dioxide induced hyper
activity. No determinations of muscle lactate were performed, as no valid sampling technique suitable for assay of carbohydrate metabolites in fish muscle in vivo was known by the authors at that time. Since then the sampling technique developed by Wollenberger et al. (1960) has been adapted by Börjesonand Fellenius1 (to be published) for accurate sampling of fish muscle. The present paper describes the use of this method for me
asurement of the lactate contents in body muscle from salmon parr during the agitation caused by a high external pC02.
II. MATERIAL AND METHODS Test fish
Second-summer parr (Salmo salar L.) weighing 25—40 g were brought from the salmon hatchery of the Fishery Board of Sweden, Älvkarleby, to Uppsala two months before the experiments.
The fish were kept in our laboratory in a 1 000 litre aquarium with streaming water (1—3 m/min) and acclimatized to the aerated Uppsala tap
1 Towards a valid technique of sampling fish muscle to determine redox substrates.
water (for quality, see Table 1). The fish were fed automatically twice a day with pellets (Salmon Grove, size 4, Astra-Ewos AB, Södertälje, Sweden).
Experimental
The fishes were placed in the test aquarium (Höglund and Härdig 1969, Fig. 2, p 84: Hög
lund and Persson 1971, Fig. 1, p 76) 24 h before the pC02 was sharply raised to about 20 mm Hg. This was achieved by adding hydro
chloric acid to the aerated tap water (see Table 1) to a pH of 6.8—6.9. After 20 min of exposure to the raised pC02 the fish was taken out and stunned by a blow on the head, and aluminium clamps cooled in liquid nitrogen (Wollenberger
et al. 1960) were pressed on the back just in front of the dorsal fin, whereby a piece of frozen muscle tissue 2 mm thick was obtained. The whole procedure, from the time of removal of the fish from the water, took about 10 seconds.
Analyses
Skin and visible bone were removed from the muscle sample which was then pulverized in liquid nitrogen as described by Lowry et al. (1964).
Lactate was determined in neutralized perchloric acid extract according to Hohorst et al. (1959).
Lactic dehydrogenase and NAD+ were obtained from Sigma Chemical Co.
Statistics
Student’s t-test was used in the statistical analyses, p <0.01 being considered significant.
III. RESULTS
The lactate estimates arrived at in the present study are presented in Table 2 along with earlier
Table 1. Chemical characteristics of the aerated tap water in the laboratory in Uppsala (Nov.
1974).*
Temp. Tr Tot. C02* 1 pC02
0(2 P^1 mM mm Hg
p02 2
as percentage of air saturation
7.9 4.5 2—3 85—90
1 Alkalinity determination according to Berger; in Karlgren (1962).
2 Oxygen determination — ordinary Winkler; in Karlgren (1962).
Table 2. Lactate content in body muscle (mmol/kg wet weight') and blood (mmol/l) of salmon parr.
Control group Fish acclimatized to aerated Uppsala water (see Table 1)
Test group
Fish exposed to pC02 of 20 mm Hg
Muscle 1 Blood 2 20 min
Muscle
0—60 min Blood 2
Mean ± SD 1.01 ± 0.53 1.08 ± 0.42 2.32 ± 0.65 1.71 ± 1.26
n 6 10 10 13
1 Data from Börjeson and Fellenius (to be published).
2 Data from Höglund and Börjeson (1971).
data from Höglund and Börjeson (1971) and Börjeson and Fellenius (in preparation). The values obtained by the latter authors may be regarded as good estimates of muscle lactate in rested salmon parr. The hyperactivity induced by raising the pC02 caused a notable increase in the muscle lactate from 1.01 to 2.32 mmol/kg wet wt (p <0.01). However, there is no statisti
cally significant difference between the lactate levels in the muscle and in the blood of the parr belonging to the test group of Table 2 (0.20 <p
< 0.10). Höglund and Börjeson (1971) found only a slight increase in the blood lactate of salmon parr exposed to a high pC02 as compared with the controls. The significance level pertaining to this difference was erroneously noted in that paper {op. cit., Table 2, p. 70). It should have been 0.20 < p < 0.10, which further supports the
* It should be noted that during the last few years the alkalinity of the tap water in Uppsala has de- creased.
statement made by these authors on p. 71. “It is concluded that the transient acidosis observed is not caused by a lactate accumulation. Accord
ingly the acidosis just seems to depend upon an unbalanced hypercapnia caused by the C02 treat
ment.” Thus, it is evident from the present study that the lactate content and pH of the blood alone do not give a complete picture of the acid- base status of the fish. The lactate content in the muscle would seem to be a more sensitive index of the metabolic acidosis due to lactate than the lactate level in the blood.
IV. DISCUSSION
The present results seem to support the view expressed by Love (1970, cf. p. 44), among others, that lactic acid is released rather slowly from fish muscle into the blood. Violent thrashing about gives rise to an increase in muscle lactate.
This increase must be considerable, however, be-
fore significant lactate accumulation can be ob
served in the blood either immediately or later.
Wittenberger (1968) found that muscular work leads to an intensification of glycolysis in the white muscle, and of oxygen consumption in the red muscle. Bilinski and Jonas (1972) noted a much higher rate of lactate oxidation in red than in white muscle from rainbow trout. This indicates that the lactate produced in the white muscle may be oxidized in the red muscle and thus partly may not be released into the blood circulation.
V. SUMMARY
The lactate content in the body muscle of salmon parr (Salmo salar L.) increases during the initial phase of hyperactivity and acidosis due to hyper
capnia deriving from a sudden rise of the pC02 in the respiratory water. This is not accompanied by any statistically significant elevation of the blood lactate level. The biological significance of this event is briefly discussed.
VI. ACKNOWLEDGMENTS
We are indebted to Professor Gunnar Svärdson.
Financial support from the Fishery Board of Sweden is appreciated.
VII. REFERENCES
Bilinski, E. and R. E. E. Jonas. 1972. Oxidation of lactate to carbon dioxide by rainbow trout Salmo gairdneri tissues. /. Fish. Res. Bd. Canad. 29 (10):
1467—1471.
Börjeson, H. and E. Fellenius. In press. Towards a
■valid technique of sampling fish muscle to deter
mine redox substrates. Acta physiol, scand. 96.
Hohorst, H. J., I. H. Kreuts and Th. Bücher. 1959.
Über Metabolitgehalte und Metabolit-Konzen
trationen in der Leber der Ratte. Biochem. Z. 332:
18—46.
Höglund, L. B. and J. Härdig. 1969. Reactions of young salmonids to sudden changes of pH, carbon dioxide tension and oxygen content. Rep. Inst.
Freshw. Res. Drottningholm 49:76—119.
— and H. Börjeson. 1971. Acidity and lactate con
tent in the blood of young Atlantic salmon Salmo salar L. exposed to high pCOa. Rep. Inst. Freshw.
Res. Drottningholm 51:67—74.
— and A. Persson. 1971. Effects of locomotor re
straint and of anaesthesia with urethane or MS-222 on the reactions of young salmon Salmo salar L.
to environmental fluctuations of pH and carbon dioxide tension. Rep. Inst. Freshw. Res. Drottning
holm 51:75—89.
Karlgren, L. 1962. Vattenkemiska analysmetoder.
Institute of Limnology, Uppsala. 115 p. (Mimeo
graphed in Swedish).
Love, M. R. 1970. The chemical biology of fishes.
Acad. Press, London and New York. 547 p.
Lowry, O. H., J. V. Passonneau, F. X. Hasselberger
and D. W. Schulz. 1964. Effect of ischemia on known substrates and cofactors of the glycolytic pathway in brain. J. Biol. Chem. 239:18—30.
Wittenberger, C. 1968. Biologie du chinchard de la mer noir (Trachurus Mediterraneus Ponticus) XV. Recherches sur le metabolism déffort chez Thrachurus et Gobius. Mar. Biol. 2:1—4.
Wollenberger, A., O. Ristan and G. Schoffa. 1960.
Eine einfache Technik der extrem schnellen Ab- külung grosserer Gewebestücke. Pflügers Arch, ges. Physiol. 270:399—412.
VIII. KEY WORDS
Lactate, muscle lactate, blood lactate, metabolic acidosis, acidosis, hypercapnia, Salmo salar.
The Acidification of Swedish Lakes
WILLIAM DICKSON
The National Swedish Environment Protection Board, Research Laboratory, Drottningholm, Sweden
I. INTRODUCTION
Sweden has about 90,000 lakes. These have a total area of about 40,000 km2 and thus occupy 9 per cent of the country (450,000 km2). The four larg
est ones, Lakes Vänern, Vättern, Mälaren and Hjälmaren, take up a quarter of this area and a further 4,000 lakes are bigger than one km2, but the majority (85,000) are smaller, accounting for 20 per cent of the total lake area.
The yearly precipitation over the country rang
es from 400 mm in the eastern parts to 1,800 mm in the mountain area in the north-west. The mean precipitation is about 700 mm.
The run-off increases from about 125 mm in the south-east to over 1,500 mm in the mountain area. The average run-off is about 400 mm per year.
Owing to different proportions between size of drainage areas and lake volumes, the theo
retical retention time for the lakes varies from several decades (Lake Vättern, 60 years) to less than two years or even one year for most lakes.
II. BEDROCK
The bedrock in Sweden consists mainly of slowly weathering granites, gneisses and porphyries. In some parts of the country, however, limestone or lime-rich greenstones (diorites, gabbroes, hy- perites, diabases and amphibolites) are found.
The occurrence of lime in rocks and soils is shown in Fig. 1 (from Magnusson et al. 1957).
Limestone and calcareous rocks are found in the following areas: Around Lakes Storsjön and Siljan; to the east of Lake Vänern and Lake Vät
tern; to the west of Lake Hjälmaren; in the southernmost part of Sweden; and on the islands Gotland and Öland.
From these areas and from the lime rocks in Fig. 1. The occurrence of lime in Sweden (from Magnusson, Lundqvist and Granlund 1957).
the Gulf of Bothnia, lime was spread — mainly south-eastwards — by the inland ice during the last glacial period, making the soils in adjacent areas more calcareous than in other parts of the country.
On some places along the coast, shell banks give a high calcium content to the soil.
III. LAKES
The bedrock and soil have a great influence on the composition of lake and ground water. In lime-rich areas, lakes will have a bicarbonate content, owing to the solution of the lime
CaC03+H,0 + CO„Ca2++ 2HCO3-, that is often of the order of 0.5—2 mekv/litre, giving a pH of 7—8. Lakes on less weathering ground will have a natural alkalinity of 0.1—0.2 mekv/litre or even less and a pH of 6—7. The majority of Swedish lakes belong to this latter group, i-e. to the soft and low-buffered waters.
In these the atmospheric contribution is responsible for the greater part of their salt content. In the mountain region several of these lakes have con
ductivities of about 10 liS, 20 C°, which is almost similar to that of distilled water.
Fig. 2 shows the alkalinity of Swedish lakes.
The map is mainly based on the results from 1,250
Alkalinity
m M
0.10 Q.25 0,50 1 2
Storsjön 0.32
Sämamanssjöarna 0
Venjansjön 0,10 Upprämen 0 Övre Fryken 0,04
Södra Boksjön 0 Vänern 0,17 Rishagerödvattnet 0
Ömmern <0,01
Bolmen 0,07
mekv/l
Ringsjön 1.52-
300 km Fig. 2. Alkalinity in Swedish lakes.
The map is mainly based on the observations in 1,250 lakes in August 1972. Alkalinites above 0.5 mekv/l.
are found in the lime-rich areas, cf. Fig. 1. Values below 0.1 mekv/l. are found in the western and south
western part, along the coast in the north and south
east of Stockholm (from Johansson and Karlgren
1974).
Table 1. Some examples of alkalinity, pH and conductivity in lakes on weath
ering and less weathering ground. (Data from Mälaren and Vänern from Ahl
1973 a and h. Cither data from the National Swedish JLnvironment Protection Board, Research Laboratory, Drottningholm, 1972—74.)
Ground Lake Size km2
Vombsjön 12.4 Bäste träsk 6.6 weathering Ringsjön 41
Vättern 1912 Mälaren 1140 Storsjön 456 Vänern 5550 Horna van 251
less Venjansjön 34
weathering Bolmen 184 övre Fryken 42
ömmern 10.3
Sö. Boksjön 9.1
Date Alkalinity
mekv/l. pH pS 20°C
Aug 1972 2.03 8.9 371
Aug 1972 2.01 7.9 234
Aug 1972 1.52 8.8 238
Sep 1972 0.54 7.7 104
1964—1971 0.53 8.0 150
Aug 1972 0.32 7.3 36
1973 0.175 7.1 80
Aug 1972 0.14 6.9 23
Aug 1972 0.10 6.9 21
Aug 1972 0.07 6.6 64
Aug 1972 0.04 6.5 26
Aug 1974 <0.01 5.5 64
Aug 1972 0 4.5 39
Table 2. Contents of salts in precipitation 1955—59 and 1970—73. Station Plönninge in the south-western part (56° 42' 12° 45') and Forshult in Central Sweden 400 km to the north (60° 05’ 13° 47’). At station Plönninge there is a general increase of salts 1970—73 compared with 1955—59 (partly local contamination). At both stations, however, a rise in sulphur and nitrogen of 50—100 per cent is noted. The alkalinity of 0—0.02 mekv/l. during 1955—59 is replaced by an excess of hydrogen ions of 0.03 mekvH. 1970—73 and a lowering of pH to 4.5. (Data from the International Meteorological Institute, University of Stockholm, 1974.)
PH H Na K Ca Mg
mekv/l
nh4 SO4 Cl NO3 Alk
Plönninge
1955—59 5.0 0 0.097 0.007 0.042 0.032 0.044 0.074 0.104 0.025 0—0.02 1970—73 4.5 0.03 0.107 0.031 0.063 0.034 0.054 0.148 0.126 0.045 0
1955—59 5.4 0 0.017 0.004 0.039 0.010 0.012 0.045 0.012 0.012 0—0.02 1970—73 4.5 0.03 0.017 0.007 0.027 0.010 0.015 0.076 0.012 0.020 0
lakes analysed in August 1972 (from Johansson
and Karlgren 1974). The good agreement be
tween alkalinity and the occurrence of lime in Fig. 1 should be noted.
Examples from some lakes on weathering and less weathering ground are given in Table 1.
IV. ACIDIFICATION Bogs
It has long been known that bog lakes can be very acid. Bog water usually has a very low salt content, which is entirely derived from the atmos
phere. The vegetation around it, mostly peat mosses, have to depend on these salts for their nutrient requirements. The uptake of cations is larger than is that of anions, and is compensated for by a corresponding release of hydrogen ions, which in turn leads to an acidification of the bog water. Together with the dissolved acid de
composition products, humic acids, this process can bring about a very low pH, as low as pH 3 in small bog pools.
Coniferous forests
A similar mechanism is considered to appear when spruce or pine is planted on former arable land. The uptake of cations and the release of hydrogen ions and acid humic substances may acidify the soil from a level even above pH 6 to values of only pH 4 within a few decades.
Oxidation
Another type of acidification occurs when sul
phide is oxidized in soil or sediment.
Hydrogen sulphide H2S+202 -*■ 2H+ + S042- Iron sulphide FeS + 20, + 2H20 ->
2H+ + Fe (0H)2+S042-.
The processes occur regularly and are considered to be very important for the weathering of the soil material. When soils that are usually sub
merged in water, come in contact with air during a long period of dry weather or low water, they will be oxidized and will acidify the next high water. Illustrative examples of this natural acidi
fication have been found in lakes surrounded by sulphide soils. In such lakes a pH decrease to 3—3.5 has been found, as well as fish kills, clarification of the water owing to the precipita
tion of humic substances, and the adaptation of an extreme plankton (Högbom 1921, Vallin 1953).
The same type of acidification, in this case man-influenced, may also occur when bogs are ditched. Here, too, fish kills have been observed (Dahl 1923).
In nitrifying soils (above pH 5), ammonium will be oxidized to nitrate with a consequent acidification
NH4+ + 20g 2H+ + NOg-+H,0
The process is well known to agriculturists and has become a problem in modern farming. The acidification from 100 kg ammonium-nitrogen requires a lime dose (CaO) of the order of 300 kg (Nömmik 1966).
Man-made atmospheric acidification
The acidification of soil and lakes due to atmos
pheric pollution by sulphur and nitrogen com
pounds has attracted increasing attention in Scandinavia during the last decade (Odén 1968, Anon. 1971). The problems are similar in Canada, where large acidifying emissions have influenced meagre soils and low-buffered lakes (Beamish
and Harvey 1972).
Today about 20 per cent of the total quantity of sulphur released into the atmosphere is emitted in Europe, from an area of only about 1 per cent of the total surface of the earth. In this region more than 75 per cent of the sulphur in the at
mosphere has an anthropogenic origin (Anon. 1971). The emission has probably increased by about 3 per cent a year (Munn and Rodhe 1971).
In Sweden the composition in air and precipi
tation has been analysed monthly since the early 1950’s by the International Meteorological Insti
tute of the University of Stockholm.
The data show a sharp decrease in pH from around 5.5 in the 1950’s to pH 4.3—4.5 up to Middle Sweden today, and an increase in sulphur and nitrogen compounds of 50—100 per cent (Table 2).
These changes are clearly connected with the continuous increase of acidic emissions and with the change-over from coal to oil combustion and from small to tall chimneys in Western Europe.
V. EFFECTS IN LAKES pH and alkalinity
Naturally there must have been a continuous increase in atmospheric pollution ever since the Industrial Revolution, with corresponding in
creased effects on waters. In Southern Norway, fish kills occurred as early as the 1920’s in waters with a pH of around 5.0 and a connection be
tween a mild, humid climate (southern winds?) and the acidity of the lakes was suspected (Sunde
1926). This area is now the most highly acidified in Scandinavia.
In Sweden, the most sensitive lakes in the West Coast region, with “natural” pH values of about 5.5—6 (almost that of rainwater), lost
lake area
Total area 6067 Nectars
number of lakes
Total number of lakes 321
4,0-4,54,6-5,0 5,1-5,5 5,6-6,0 >6,0 pH Fig. 3. pH in 321 lakes around Gothenburg during 1968—70. 85 per cent of the lake area had a pH of 5.5 or lower. 53 per cent of the total number of lakes even had a pH of 4.0—4.5 (from Schmuul 1972).
their roach population in the 1930’s possibly on account of the atmospheric acidification. “Clean rainwater” has a pH of about 5.6 and the roach will be affected already at values just below pH 5.5 (Almer 1972).
During the last 20 years a large number of Swedish lakes have been acidified. Trends of the
“Surface Water Network” in Sweden (Odén
and Ahl 1972) indicate that “if the present development continues, in less than 50 years about 50 per cent of our lakes and rivers may have pH values of 5.5 or even 5.0” (Anon. 1971).
This situation occurred long ago in the region around Gothenburg on the West Coast, which not only is extremely sensitive but also repre
sents the most exposed area of Sweden. Of 321 lakes investigated during 1968—70, 93 per cent had pH 5.5 or lower and 53 per cent even had 4.0—4.5. Of the corresponding lake area, 85 per
number of lakes
summer values 1971
summer values 1930- & 40'ies
4,5 5,0 5,5 6,0 6,5 7,0 7,5 8,0 pH Fig. 4. pH change in West Coast lakes. Values from 1971 were often 1.5 pH units lower than during the 1930s and 40s in the same lakes.
cent had pH 5.5 or lower (Fig. 3, from Schmuul
1972).
A similar picture is found in the whole West Coast region. Extrapolated from the findings 1970—72 (Table 3, from Almer et al. 1974), half of the number of lakes in the area, about 1,500 of a total of 3,000, would have a pH
lower than 6, and some 800—900 would have pH values even lower than 5.0. In these lakes, the values had been lowered by up to 1.8 pH units from the 1930’s and 40’s to summer 1971 (Figs. 4 and 5).
The atmospheric pollution can be followed further north in almost the whole of Sweden, all lakes and rivers being affected, to a greater or lesser extent. Those with natural alkalinities below 0.1 mekv/litre are the most sensitive and they are the first where the pH will drop (Fig.
6). Most of them are located in the western part of the country (Fig. 2). They may have an area of several square kilometres. The total number of lakes now acidified to below pH 6 is probably around ten thousand and the number below pH 5.5 five thousand. Thousands will now have alkalinities of 0—0.05 mekv/litre and pH reduced by 0.5—1 unit.
The most acidified lakes are often located in the upper parts of a lake system, thus having small drainage areas and not being subjected to influence from agricultural land.
Conductivity and ionic composition
In Southern Sweden, since the 1930’s and 40’s, the conductivity in lakes has risen by 10—30 pS
Transparency (m)
transparency.
Fig. 5. Lake Stora Skarsjön.
Size 0.6 km2 (58° 13' 11°:
56'). From 1943 to 1973 the pH decreased from 6.25 to 4.5. The transparency in
creased more than 7 metres (from Almer et al. 1974).
alkalinity 0,078 mekv per litre (Lake Lygnern 32,6 km2)
alkalinity 0,466 mekv per litre (Lake Norra Sämsjön 9,2 km2)
mekv acid Fig. 6. The low-buffered lake, with an alkalinity of 0.078 mekv/1., needs only one sixth of the amount of acid added to the strongly-buffered lake to reach pH 5.0. Below this pH almost all bicarbonate is lost and pH will fall drastically in both lakes when more acid is added.
(20° C) and in Northern Sweden by 5 p,S. The increase in sulphate is 0.1—0.3 mekv/litre and this accords well with the increased deposition.
In many cases there is also noted an increase of cations, which is probably connected with the leaching activity of the acids.
In the so-called “Standard Composition” of lakes (Rodhe 1949), bicarbonate is the most abundant anion and the ratio of bicarbonate to sulphate is 4.7:1. The increase — at least a twofold one — in sulphate, and the decrease in bicarbonate have considerably reduced the va
lidity of the “Standard Composition” as far as most Swedish lakes are concerned. The ratio of bicarbonate to sulphate is now usually less than 1:1.
Transparency and nutrients
Along with the acidification, the lakes will be clarified owing to precipitation of humic sub
stances and a decrease in the plankton flora (Almer et al. 1974). In some cases the trans
parency has increased by ten metres during the last thirty years.
pH 8,0
Ô 0,1 0,2 0,3 0,4 0,5 0,6 AI mg per litre
Fig. 7. Aluminium content in clear-water lakes. The solubility rises at low pH.
The content of phosphorus is very low, 2—10 pg/litre, possibly owing to the increasing precipi
tation of humus and a decreased decomposition of humus and detritus. The nitrogen content varies considerably according to the atmospheric fall-out; it ranges between 0.1 and 0.4 mg N/litre.
A high proportion of this remains as nitrate even during the summer, owing to the low plankton activity.
Solution of aluminium and manganese
The content of aluminium rises in acidified lakes and is 0.2—0.6 mg Al/litre (0.01—0.07 mekv), whereas clear-water lakes with a normal pH have 0.05 mg/litre or less (Fig. 7). Below pH 5, alumi
nium will probably occur as a tri- or bivalent cation, but in less acid water it will exist in a monovalent or a non-ionic form (Pionke and Corey 1967, Malmer 1974). Manganese, too, goes into solution in acid water, and a high con
tent, 0.3—0.4 mg/litre (Fig. 8), appears in the
PH 8,0
5,0 • • j
0,1 0,2 0,3 0,4 Mn mg per litre
Fig. 8. Manganese in lakes. A considerable increase in solubility appears at about pH 4.5.
50
. * •“
Table 3. pH in lakes on the West Coast 1970—72, within 80 km from the sea.
The total number of lakes in the region is about 3,000. Extrapolated from the lakes examined, some 1,500 would have a pH below 6 and 800—-900 a pH below 5 (from Almer et al. 1974).
PH
Number of lakes November— April—
December, 1970 June, 1971 August, 1972
<3.9 15 4 3
4.0—4.9 97 79 17
5.0—5.9 67 129 35
6.0—6.9 116 124 63
>7.0 19 47 43
No. of lakes
studied 314 383 161
<5.0 36 per cent 22 per cent 12 per cent
<6.0 57 per cent 55 per cent 34 per cent
most acid lakes (corresponding to about 0.01 mekv/litre). No increased solubility of iron or silicon has been observed, so far as is known.
Composition of precipitation and lakes, three examples
The water chemistry of most of the Swedish lakes on primary rocks is influenced to a marked extent by the atmospheric contributions. Three examples from different parts of Sweden will illustrate this.
West Coast area
The precipitation around Gothenburg and the industrialized areas in this region is very acid, with a pH of about 4.2 (1973). The precipitation amounts to about 700 mm per year, and évapo
transpiration will concentrate it about 1.6—1.8 times. The composition of the water of three forest lakes and some calculations of the possible contributions are made in Table 4.
The content of chloride in the lakes near the coast, 20 km from the sea, 100 metres above sea level, but below the highest shoreline of the sea, is 0.35 mekv/litre, or more than twice the amount that comes with precipitation (0.15 mekv).
Even lakes above the highest shoreline have the same content of chloride. So in this area the dry deposition of sea salts will be equal or greater (about 1.0—1.5 times) than the amount from precipitation.
Of the sulphate content, 0.34 mekv/litre, some 0.16 mekv is derived from precipitation. To this must be added a small fraction, which is derived from sea spray (0.02 mekv/litre), while probably the greater part of the rest, 0.16 mekv/litre, is of anthropogenic origin airborne sulphur dioxide and sulphate. The total increase in sulphate, in
cluding the increase from precipitation, at least 0.1 mekv/litre, since a natural stage, is probably of the order of 0.2—0.3 mekv/litre.
The content of nitrate in precipitation is about twice as great as that in the precipitation of the 1950’s, and ammonium has increased by around 25 per cent (Table 2). The concentrated deposition of ammonium and nitrate with precipitation (2.4 mg N/litre) is six times as great as that found in lakes (0.4 mg Total N/litre). The soil and forests evidently have a considerable ability to retain the nutrients needed.
There seems, however, to be a very consider
able leaching of cations, calcium, magnesium, sodium, potassium and aluminium to the lakes (up to 0.25 mekv/litre) to compensate for the increased deposition of acid, sulphur and nitrogen.
The hydrogen ion concentration in lakes at pH 4.9, for instance, is 0.09 mekv/litre less than what comes from precipitation, and to compensate for the sulphur a further 0.16 mekv of cations per litre is required (Table 4). Part of the amount of cations and sulphate may have leached out when
Table4.ContentsofsaltsinthreelakesintheWestCoastarea,(58°12°)locatedabout20kmfromtheseaandwithin15km
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Table 5. Rishagerödvattnet near Stenungsund and Gothenburg in the West Coast area (58° 07' 12° 00'). Mean values from. 1947—52 (Lysén 1960) and 1972—74.
Ca+Mg Alk SO4
mekv/1.
Cl
PH pS/
20° C
Colour mgPt/1.
1947—52 0.17 0.03 about 0.41 5.8 55 45
0.1
1972—74 0.33 -0.01 0.33 0.40 4.9 89 15
ammonium and nitrate are fixed in the soil. The natural additions to these lakes are very small.
Since 1947—52 the conductivity in one of these lakes has risen from 55 to 89 pS, with a corre
sponding ionic increase of 0.16 mekv of calcium- magnesium per litre, and probably some 0.2—0.25 mekv of sulphate per litre (Table 5).
Lakes with less lime and a lower capability of cation leaching will, of course, be more acidified and consequently have pH 4—4.5.
The aluminium content in the lakes (pH 4.9) is around 0.17 mg/litre, corresponding to about 0.01 mekv as a bivalent ion (A1 (OH)2+) or 0.02 mekv as a trivalent ion (Al3+). The manganese content is around 0.1 mg/litre (0.004 mekv Mn2+/litre).
Central Sweden
Lake Upprämen (60° 22' 13° 53') is situated 447 metres above sea level (and above the highest shoreline of the sea) and has a size of 3.8 km2, corresponding to about 31 per cent of its drainage area. The yearly precipitation is about 800 mm and the run-off is of the order of 500 mm. The salts from precipitation will then be concentrated 1.5—1.7 times (Table 6).
When these concentrated values of the precipi
tation are compared with those of the lake (Table 6), one finds that if all chloride in the lake (0.03 mekv/litre) is derived from the atmosphere, which is plausible (Eriksson 1955, 1960), the dry depo
sition (0.01 mekv/litre), will be much less than in the West Coast area and will represent about 0.5—0.6 of the wet deposition.
Potassium is a nutrient retained by the vege
tation and the lake has even less than what comes from precipitation. Still more evident is the re
tention of nitrogen. Only half of what is derived from the precipitation, 0.78 mg/litre, is to be found in the lake (0.4 mg Total N per litre).
Of the sulphate in the lake, 0.14 mekv/litre, 0.12 mekv is derived from precipitation and the small remainder, 0.01—0.02 mekv, may have come from dry deposition or from leaching. The lake content in a “natural” stage probably did not exceed 0.04 mekv/litre, and the increase since then should be at least three fold. Since 1955—59 there may have been a doubling (Table 2).
The content of calcium-magnesium in the lake is only 0.09 mekv/litre and at least two thirds of it is derived from the atmosphere.
One third of the water supply to the lake is deposited on the water surface as unneutralized precipitation with a pH of 4.5, and the leaching to the lake of bicarbonate from the ground is far from sufficient to compensate for all the acid contributions. The pH of the lake is now 4.7, i.e.
too acid for the stock of Arctic char, which has died out.
Lake Fjällrämen 20 km downstream has a pH of 5.4 (a decrease of 0.02 mekv/litre hydrogen ions) and 0.02 mekv of calcium-magnesium more per litre. The content of sodium and potassium is also higher.
In the clear-water lake, Upprämen, some 0.18 mg of aluminium is found, corresponding to 0.02
—0.01 mekv of Al3+ and Al(OH)2+, whereas Lake Fjällrämen, with a pH of 5.4 and rather brownish water, has 0.24 mg of aluminium, probably mostly bound to humic substances.
The precipitation values come from a station 50 km south of Lake Upprämen (Forshult, Hag- fors), and Fig. 9 shows the trend of pH since
Precipitation, Forshult
year
Precipitation, T rysil
1957 60 year
Figs. 9 above and 10 below. pH in precipitation at Forshult, Värmland (60° 05' 13° 47') and Trysil, Norway (61° 20' 12° 15'). (Data from the Inter
national Meteorological Institute, University of Stock
holm 1974.)
1955. The pH has dropped from 5.9 to 4.5 (International Meteorological Institute, University of Stockholm, 1974).
Mountain region
The lakes considered are the Särnamannasjöarna (61° 36' 12° 45') in the most southerly mountain area of Sweden. During the winter of 1972 the snow profile had a pH of 4.2 and contained twice as much sulphate and more than twice as much nitrate, ammonium and phosphorus as the lakes, where the pH was 4.9—5.0 (Table 7). The contents in the lakes rose, however, when the snow melted, and the pH dropped to 4.5. In July the pH had risen to 4.9 again.
In April 1964 a pH value of 5.4 was measured (Puke 1971, Andersson et al. 1971) and in April 1973 a value of 4.5 was recorded. The trend in precipitation has been the same (Fig. 10, Station Trysil, Norway).
At springtime, when the snow accumulated during the winter melts within a short time, there usually occurs a sharp drop of pH in low- buffered waters and this may cause kills of the fish fry, while pH during the rest of the year may be tolerable.
These three examples show the extreme depen
dence of the composition of lake waters on the precipitation. The anions, with the exception of bicarbonate (if there is any), may all derive from the atmosphere, and the same is true for nitrogen and phosphorus. An increased leaching of the cations occurs, however, probably to compensate for the increased acid deposition. But the leaching of cations and bicarbonate is often not sufficient, and this results in an acidification of the water.
Heavy metals
Parallel with this large-scale acidification, there is an increased deposition of heavy metals. The content in precipitation is several times higher than that found in lake water.
Table 8 shows the composition in precipitation during the winter 1972—73 at Drottningholm, 10 km from the centre of Stockholm. The content of cadmium (7 pg/1) was at least ten times greater than that found in lakes and the content of lead (64 pg/1) was from ten to fifty times greater.
Though there is probably an influence from Stock
holm, the values should nevertheless not be quite unrepresentative for certain areas of Southern Sweden. Snow investigations in Norway show 2
